Research that gets to the point

Stone forests are as mysterious as they are majestic.  It is not certain exactly what forces created the rock formations resembling trees found in many parts of the world, but perhaps most famously in Shilin, China.

In an experiment, a dissolving block of candy develops into an array of sharp spikes. The block starts out with internal pores and is entirely underwater. Credit: NYU’s Applied Mathematics Lab

Now a team of mathematicians has shed new light on the matter, using high-tech simulations and simple blocks of sugar to show, they say, how flowing water carves ultra-sharp spikes in landforms.

Writing in the journal Proceedings of the National Academy of Sciences, they suggest this also offers promise for the manufacturing of sharp-tipped structures, such as the micro-needles and probes needed for scientific research and medical procedures.

200909 forest spikes
A false-colour photograph of a “forest” of candy pinnacles. Credit: NYU’s Applied Mathematics Lab

The work was carried out at New York University’s Courant Institute of Mathematical Sciences.

The researchers first simulated the formation of pinnacles over time through a mathematical model and computer simulations that took into account how dissolving produces flows and how these flows also affect dissolving and thus reshaping of a formation.

To confirm the validity of their simulations, they then ran a series of experiments replicating the formation of these natural structures by creating sugar-based pinnacles, mimicking soluble rocks that compose karst and similar topographies, and submerging them in tanks of water.

No flows had to be imposed, they say, since the dissolving process itself created the flow patterns needed to carve spikes.

The experimental results reflected those of the simulations. The authors speculate that these same events happen – albeit far more slowly – when minerals are submerged under water, which later recedes to reveal stone pinnacles and stone forests.

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